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Direct and Indirect Search for Dark Matter

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Direct and Indirect Search for Dark Matter Andrzej Sołtan Institute for Nuclear Studies Direct and Indirect Search for Dark Matter Piotr Mijakowski Ph.D. thesis written under supervision of Prof. dr hab. Ewa Rondio February 2011 Abstract Direct and indirect searches for dark matter (DM) particles are discussed. The search for a diffuse signal from DM annihilation in the Milky Way is presented using the atmospheric neutrino data from Super-Kamiokande-I, -II, -III. The analysis focuses on the model inde- pendent scenario with DM particles annihilating directly into pairs of neutrinos and anti- neutrinos. No signal contribution is allowed by the Super-Kamiokande data for considered masses of DM particles in the range from 3 GeV to 3 TeV. The upper limit on DM-induced neutrino flux has been obtained as a function of the mass of relic particles. The corre- sponding limit on the DM self-annihilation cross section hσAV i has been evaluated. With this analysis, the existing limit on the value of hσAV i has been significantly improved for DM particle masses below 100 GeV as compared to previous constraints based on neutrino interactions data. Presented search can be also related to the concept of the decay of DM particles. The limit on DM decay lifetime τDM has been derived. Finally, studies related to direct DM detection are presented. The results of simulations of neutron background for the Argon Dark Matter (ArDM) experiment are shown. Contents List of Figures v List of Tables ix List of Abbreviations xi Acknowledgements xv Introduction 1 1 Dark Matter 4 1.1 Dark Matter in the Universe . 4 1.2 Standard Cosmological Model . 5 1.3 Dark Matter Candidates . 7 1.3.1 Neutralino – Supersymmetric Dark Matter Candidate . 8 1.4 Overview of WIMP Searches . 10 1.5 Direct Detection . 10 1.5.1 Status of Direct Detection Experiments . 12 1.6 Indirect Detection . 14 1.6.1 Status of Indirect Detection Experiments . 16 1.7 Summary of Dark Matter Searches . 18 2 Neutrinos 20 2.1 Introduction . 20 2.2 Neutrino Interactions with Matter . 20 2.3 Neutrino Oscillations . 25 2.3.1 Neutrino Oscillation Formalism . 26 2.4 Neutrino Sources . 28 2.4.1 Natural sources . 29 2.4.2 Artificial sources . 32 2.5 Atmospheric Neutrino Properties . 33 3 Neutrinos from Dark Matter Annihilation 37 3.1 Neutrinos from DM Annihilation in Earth, Sun and Galactic Center . 38 3.1.1 Results from Super-Kamiokande . 39 3.1.2 Comparison with Direct Detection Results . 42 3.2 Neutrinos from Diffuse Dark Matter Annihilation . 45 3.2.1 Galactic Neutrino Flux from Dark Matter Annihilation . 46 3.2.2 Limit on Dark Matter Self-Annihilation Cross Section . 51 3.2.3 Prospects for Dark Matter Diffuse Annihilation Search . 51 3.3 Neutrinos from Dark Matter Decay . 52 4 Super-Kamiokande Detector 54 4.1 Introduction . 54 4.2 Principle of Operation . 56 4.3 History . 60 4.4 DAQ Monitoring Software for SK-IV . 61 5 Atmospheric Neutrinos at Super-Kamiokande 63 5.1 Data Samples . 63 5.2 Data Selection . 67 5.3 Monte Carlo Simulation of Atmospheric Neutrino Interactions . 70 5.4 Monte Carlo Simulation of Tau Neutrino Interactions . 72 5.5 Atmospheric Neutrino Oscillation Analysis . 73 5.5.1 Livetime of Data Samples . 73 5.5.2 Fit . 73 5.5.3 Sources of systematic uncertainty . 76 5.5.4 Results . 76 6 Methodology of Search for Diffuse Dark Matter Annihilation Signal 78 6.1 Introduction . 78 6.2 Simulation of Diffuse Dark Matter Annihilation Signal . 79 6.3 Methodology . 84 6.4 Search for Low Energy Signal . 85 6.5 Search for High Energy Signal . 91 6.6 Upper Limit on Fitted Number of DM-Induced Neutrinos . 93 6.7 Summary . 96 7 Search for Diffuse DM Annihilation Signal at Super-Kamiokande 97 7.1 Diffuse Dark Matter Annihilation Search . 97 7.1.1 Data Sample . 98 7.1.2 Dark Matter Induced Signal . 98 7.1.3 Fit . 103 7.2 Fitted Number of Dark Matter Induced Neutrinos . 105 7.2.1 Upper Limit on DM-Induced Neutrinos . 107 7.3 Upper Limit on DM-Induced Neutrino Flux . 107 7.4 Limit on Dark Matter Lifetime . 109 7.5 Limit on Dark Matter Self-Annihilation Cross Section . 110 8 Neutron Background Studies for ArDM 114 8.1 Dark Matter Search with ArDM Detector . 114 8.1.1 Detector Description . 114 8.1.2 Experimental Background . 116 8.1.3 ArDM prospects . 117 8.2 Neutron Background Studies . 118 8.2.1 Rock Neutron Simulations for Canfranc . 119 8.2.2 Muon-Induced Neutron Simulations . 124 8.2.3 Conclusions on the neutron background studies for ArDM . 126 Summary and outlook 128 Bibliography 130 List of Figures 1.1 Best fit power law ΛCDM model as compared to the temperature of angular power spectrum measured by WMAP. 6 1.2 Comoving number density of a thermal relic particle in the early Universe. 7 1.3 Feynman diagrams which contribute to neutralino-quark scalar interactions (spin-independent). 9 1.4 Feynman diagrams which contribute to neutralino-quark axial vector in- teractions (spin-dependent). 9 1.5 Different ideas for DM particle detection. 10 1.6 Illustration of various detection methods of a recoil energy. 11 1.7 Annual modulation of a signal from DAMA experiment. 12 1.8 Upper limits on the value of spin-independent WIMP-nucleon cross section as a function of WIMP mass. 14 1.9 Gamma spectrum obtained in the analysis of EGRET data. 16 1.10 Positron fraction and antiproton to proton ratio measurements in the cos- mic rays by PAMELA. 17 1.11 Energy spectrum of (e+ + e−) obtained by ATIC . 18 1.12 The FERMI LAT cosmic ray electron spectrum and gamma spectrum . 19 2.1 Ratio of total charged current neutrino cross section and neutrino energy (σT /Eν) for the muon neutrinos and anti-neutrinos interacting on nucleons as a function of neutrino energy. 21 2.2 Examples of interactions involving neutrinos. 22 2.3 Relation between direction of a charged lepton produced in neutrino inter- action and direction of a parent neutrino. 23 2.4 Contribution from different processes to charged current νµ interactions as a function of neutrino energy. 24 2.5 Energy spectra and fluxes of neutrinos at the surface of the Earth calculated for different neutrino sources. 30 2.6 Schematic view of neutrinos’ creation in the atmosphere. 31 2.7 Atmospheric neutrino energy spectrum for (νµ +ν ¯µ) and flux ratio of (νµ + ν¯µ) to (νe +ν ¯e).................................. 34 2.8 The flux of atmospheric neutrinos versus zenith angle calculated for Kamioka Observatory location for several neutrino energies. 35 3.1 Illustration of a cone half-angle Φ used to investigate the value of neutrino flux from a given angular region around the position of DM annihilation source. 39 3.2 Zenith angle distributions of upward through-going muons at Super-K based on 1679.6 live days of exposure. Distributions with respect to the center of the Earth (a), the Sun (b) and the Galactic Center (c) are shown. 40 3.3 Super-Kamiokande DM-induced upward-going muon flux limits as a func- tion of Mχ for neutralino annihilations in the Earth’s core (a), the Sun’s core (b) and in the Galactic Center (c). 41 3.4 Upper limit on WIMP-nucleon cross section for spin-idependent interac- tions obtained in the analysis of upward-going muon events at Super- Kamiokande. 43 3.5 Upper limit on WIMP-nucleon cross section for spin-dependent interactions obtained in the analysis of upward-going muon events at Super-Kamiokande. 44 3.6 Illustration of expected signal from the diffuse annihilation of a 100 GeV DM particle. 45 3.7 Dark matter density as a function of radius for different halo profiles con- sidered. 47 3.8 Illustration of line of sight l and viewing angle ψ in the coordinate system related to the Galactic Center. 48 3.9 Line of sight integration J (ψ) as a function of the pointing angle ψ with respect to the Galactic Center and its average, J∆Ω, inside a cone with half-angle ψ around the GC as a function of the visible fraction of the whole sky. 50 3.10 Upper limit on the DM total self-annihilation cross section hσAV i from various components of the Milky Way halo from Ref. [90]. 52 4.1 A schematic view of the Super-Kamiokande detector and the experimental hall. 55 4.2 Construction of the wavefront of Cherenkov radiation. 56 4.3 Inside view of the Super-Kamiokande detector during the maintenance in 2006 and illustration of Cherenkov ring produced in a charged current νe interaction in water. 57 4.4 An example event display of a single-ring µ-like and e-like events. 58 4.5 Particle identification likelihood distribution (PID). 59 4.6 Skhist application window. 62 5.1 The simulated parent neutrino energy distributions for the fully-contained, partially-contained, upward stopping muon and upward through-going muon event samples of atmospheric neutrinos. 66 5.2 The number of hits in the largest outer detector cluster (nhitac). 68 5.3 An example of event display of partially-contained and upward thruogh- going muon events. 69 5.4 The illustration of the zenith angle and momentum distributions of the data samples used in the neutrino oscillation analysis. 75 2 2 5.5 Best fit contour for the values ∆m23 and sin 2θ23 oscillation parameters in the 2 flavor analysis of SK-I+II+III data. ..
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